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Monday, February 28, 2011

This time next week, the next planetary Decadal Survey covering the years 2013-2022 will be public. NASA has said that it will take its recommendations as its priorities, and Congress has shown deference to to the Surveys in allocating funds. This Survey's report, "Visions and Voyages: Planetary Science in the Coming Decade," is likely to be both in-depth and long. With this post, I'll begin discussing what I consider to be the key issues the Survey is likely to address. Like a pre-game analysis, my goal is not to make specific predictions (why prove myself wrong in print?), but rather suggest pointers of what to look for. And I'll allow myself the fun and hubris in one post of stating what I would have recommended should anyone have asked. I'll also report on the poll in which you have voted for the missions you would like to see prioritized.

The Decadal Survey reports run hundreds of pages. Often, much of text is devoted to summarizing current state of our knowledge and stating key questions to answer. The topics that are likely to receive the greatest focus, however, will be the prioritized list of questions to pursue and the recommended missions to address them. With that in mind, here are the questions that I will have in mind as I review the report:

1. What budget is assumed? Budget issues have led NASA to consider replacing its own mission for the top priority of the just completed astronomy and astrophysics Decadal Survey, the WFIRST dark energy and exoplanet mission, to seek a partnership on a similar proposed ESA mission. NASA reportedly has also dropped plans for two missions prioritized by the Earth Science Decadal Survey, CLARREO and DESDynI, for lack of expected funding. While the reasons for these decisions are more complicated than simply too little money in NASA's budget, these are cautionary tales. The recent astronomy and astrophysics Survey members assumed that the upside budget was current funding adjusted for inflation and the downside was current funding eroded by inflation. An extension of this year's planetary funding for the coming decade could support a major flagship mission, perhaps a smaller flagship mission, and several New Frontiers and Discovery missions. An assumption of the budget plans in this year's FY12 budget plan with its declining budgets might mean a program of New Frontiers and Discovery missions.

2. What are the major science questions that are prioritized? The Survey might prioritize understanding the early history of terrestrial planets and potential for early life, leading to a high priority for the series of missions (>$6B in total) leading to a Mars sample return. Alternatively, the Survey might prioritize investigating icy-ocean moons as potential habitats for life, leading to a high priority for the Jupiter Europa Orbiter and New Frontiers missions to the outer planets. As a third possibility, the Survey might emphasize a balance of questions leading to more modest missions to a number of targets, but no major flagship missions to any one. The assumed budget determines the scale and/or number of questions that can be addressed, but the prioritized questions lead directly to the missions that receive priority recommendations within that budget.

3. What is the proposed mixture of more modest Principal Investor (PI) led missions and major institution-led Flagship missions? There has always been a tension between doing a small number of big missions and a larger number of small missions. Big missions can address questions that smaller missions cannot, but more smaller missions can partially address a wider range of questions and targets. The recent astronomy and astrophysics Decadal Survey recommended completion of one gigantic mission, the James Webb Space Telescope, one modest Flagship scale mission, and prioritized increasing the number of small PI-led missions. Big missions have an advantage that they can create their own momentum, but can also consume budgets if funds are cut or cost overruns occur. Small missions may be a more robust strategy in face of tight budgets, but may also not be easier to not fund (which would you prefer to pitch to a Congressman to fund: Mars sample return, Jupiter Europa Orbiter, or the selection of the 15th Discovery mission?)

4. What technologies are prioritized for development? Planetary exploration is an inherently high tech field. The missions that can fly can be only as good as the technologies that are ready to fly. Developing new technologies often requires years of research, prototypes, and testing before a technology becomes ready for flight. The technologies that the Survey prioritizes are the seeds for the missions that will fly in the decade of the 2020s.

Friday, February 25, 2011

ESA announced a list of four missions as candidates for its next medium class mission slot for launch in the early 2020s. Two missions relevant to planetary selection were included. Several others, including the Titan Aerial Explorer balloon mission and a Uranus Pathfinder orbiter mission were not selected.

The two planetary-related proposals are:

"MarcoPolo-R is a mission to return a sample of material from a primitive near-Earth asteroid (NEA) for detailed analysis in ground-based laboratories. The scientific data would help to answer key questions about the processes that occurred during planet formation and the evolution of the rocks which were the building blocks of terrestrial planets. The mission would also reveal whether NEAs contain pre-solar material not yet found in meteorite samples, determine the nature and origin of the organic compounds they contain, and possibly shed light on the origin of molecules necessary for life.

"The Exoplanet Characterisation Observatory (EChO) would be the first dedicated mission to investigate exoplanetary atmospheres, addressing the suitability of those planets for life and placing our Solar System in context. Orbiting around the L2 Lagrange point, 1.5 million km from Earth in the anti-sunward direction, EChO would provide high resolution, multi-wavelength spectroscopic observations. It would measure the atmospheric composition, temperature and albedo of a representative sample of known exoplanets, constrain models of their internal structure and improve our understanding of how planets form and evolve."

Also on the candidate list are the Large Observatory For X-ray Timing (LOFT) and the Space-Time Explorer and Quantum Equivalence Principle Space Test (STE-QUEST) proposals.

Monday, February 21, 2011

With this post, I'll complete the longer summaries of the Decadal Survey mission concepts. Barring breaking news, the next post will provide shorter summaries for several remaining concepts.

While two mission studies plus the SAGE New Frontiers proposal looked at landed missions, the Venus Climate Mission (VCM) would focus on the atmosphere.

The design of the VCM mission is to provide answers to the outstanding science questions about Venus' super-greenhouse gas climate system. Previous missions have left numerous questions unanswered: "VCM will resolve current uncertainties in atmospheric motions, radiation balance, cloud composition and chemistry, while also making elemental and isotopic measurements that will reveal the origin and evolution of the atmosphere and the evolution of the extreme greenhouse climate." A key goal will be to understand the relationships and feedbacks between these parameters to enable modeling of Venus' climate and other Earth-like planets. Another key goal will be to understand how Venus' atmosphere transitioned from what is believed to have been Earth-like to the current extreme CO2 dominated greenhouse.

Winds would be expected to carry the balloon system in a spiral to the pole allowing the study across a range of latitudes.

Previous missions have shown that Venus' atmosphere and weather patterns are highly variable across space and time. The goal of VCM "will be the first ever truly 3-dimensional (and to a large extent 4-dimensional, including many measurements of temporal changes) characterization of Venus’s atmosphere." VCM would combine several different platforms to examine the atmosphere from the cloud tops to the surface. A gondola balloon system would float at 55.5 km altitude for long term studies of atmospheric composition, structure, and winds. A mini-probe would be dropped from the balloon system at the initial entry to descend to the surface to study composition, atmospheric structure, and winds. Two small drop sondes would be released from the gondola over the course of its 21 day mission to probe structure and wind from the float altitude to the surface at different latitudes and times of day or night. A camera on the data relay orbiter would track high altitude cloud movements.

The in-situ VCM elements. The mini-probe would be released on deployment and the helium tanks would be dropped after balloon inflation. The drop sondes would be released later to sample different atmospheric conditions from the float altitude to the surface.

Put together, "Simultaneous dynamical measurements from the Gondola/Balloon system and the Mini-Probe and Drop Sondes will allow, for the first time, concurrent measurements of vertical dynamics, cloud particle size and density, and cloud forming species over a wide range of longitudes, solar zenith angles, altitudes and times."

Overall cost of the mission is estimated to fall between approximately $1.1B and $1.6B, which would be slightly more than a New Frontiers mission to a smaller Flagship mission.

Several missions to continue the exploration of Venus' atmosphere from within the atmosphere have been put forward over the last decade. They range from just a descent probe or a balloon-gondola only platform to multi-element concepts similar to VCM. The European Venus Explorer (EVE) mission would use international collaboration to deliver a set of platforms that would in many ways be more capable than VCM. ESA would provide an orbiter with a number instruments to remotely study the atmosphere and surface along with a balloon/gondola that in a summary appears similar to VCM's. Russia would provide the launch vehicle and a descent probe that would also be a lander. Japan might provide an additional balloon platform to operate at a different altitude.

Editorial Thoughts: Repeated studies have proposed similar sets of mission elements to answer the key questions about Venus' atmosphere and climate. The proposals have differed primarily in how many elements were included in response to the possible funding. Given the climate change occurring on our planet, studying Venus' climate seems a priority to me. The multi-platforms called for in these proposals would make an international collaboration reasonably straightforward. NASA, for example, might provide a more capable orbiter, a second descent probe/lander for an EVE, or additional balloons. Alternatively, Europe could provide a more capable orbiter to compliment VCM's balloon/gondola and descent platforms. Russia's planned lander would complement either scenario as would NASA's SAGE lander if selected.

Saturday, February 19, 2011

The following letter from Dr. James Green, NASA's Director of Planetary Science, has written a letter posted yesterday explaining NASA's recently proposed budget and the upcoming release of the Decadal Survey report on March 7.

Dr. Green explains that the decline in the planetary science projected budget in coming years is a result of NASA not being able to include the recommendations of the Decadal Survey in the budget submission. After the release of the report, NASA will "create a new program structure" that will be reflected in future budget submissions. He cautions, however, that in the current political climate that, "no one know what Planetary's FY 2012 budget or out year profile [projected future budgets] ... will be once enacted."

Editorial Note: Dr. Green's letter clarifies that the projected budgets for years beyond the current FY12 budget may be increased if necessary to accommodate the Survey's recommendations. The notes in the budget documents from which I drew my analysis suggested this possibility, but in a political climate promoting flat or declining budgets for federal programs, I did not place sufficient emphasis on this. I stand corrected, and this position is more encouraging for a vigorous program in the coming decade.

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LETTER FROM DR. JAMES GREEN
Dr. James Green writes about the NASA’s budget and anticipation of the Planetary Science Decadal Survey
Feb. 14, 2011

The President submits his budget to Congress on February 14th. This is a highly constrained budget for NASA taking into account the economic and political times. The Administration has had to make some tough decisions in nearly every area of NASA’s activities resulting in cutbacks or even eliminating some elements. Since we still don’t have a passed FY 2011 budget, the Administration calls the NASA budget from FY 2012-2016 a “notional budget.”

The Planetary Science Division budget just submitted has several important features for everyone to take note. First, although the top line run-out numbers are below the President’s budget projection of last year, the budget in FY 2012 is very healthy and is an adequate budget in a year for which we launch and land the Mars Science Laboratory (MSL), the most challenging scientific and engineering Mars mission ever! Secondly, it is a budget that is in anticipation of the Planetary Science Decadal Survey and; therefore, all potential new strategic missions, regardless of destination are not included in the out years.

Because the Administration is waiting for the results from the Planetary Science Decadal Survey, our out year budget decreases with time through FY 2016. The Planetary Decadal is for the years 2013 to 2022. After the Decadal is released, we will fill in the details, create a new program structure, and step up to the challenges of the next decade’s missions. That said, no one knows what Planetary’s FY 2012 budget or out year profile, just delivered to Congress, will be once enacted. Such is the nature of the times we find ourselves in.

So here is how we must begin to build the next decade’s planetary program. When the survey is released on March 7th (the current projected date), the Division of Planetary Science (DPS) is working with the Decadal Chair, Steve Squyres, to communicate what’s in the Survey, beginning with the planned roll-out at the Lunar and Planetary Science Conference in Houston, through town hall meetings around the country and numerous other ways. My NASA Planetary Sciences team will support this roll-out in every way we can. Why? Over the last two years, we all have invested heavily in support of this Survey. Hundreds of hours have been devoted supporting Dr. Squyres, his committee and subcommittees, with input from over 1600 planetary scientists across the world. I view this Survey as not only reflective of the next decade’s path forward, but also a validation of the foundation we have been building over the past decades. Each mission, each discovery, each success we have made across our planetary portfolio has been another brick in that foundation. Moreover, this Survey will serve as a guidepost to those early career scientists, engineers, and even high school students in making their career decisions and/or trade-offs in their research interests. So, this Survey serves as not just another report in my view, it is a prospectus representing Planetary Sciences’ mutual investment for our future.
I challenge everyone in the community to see themselves and their role in the support of the Survey. My plan is to provide a response before the end of this Fiscal Year. Yes, this is optimistic, but we have a narrow budget process window and also have three launches to focus on. As always, I will continue to solicit your feedback and advice as we begin to implement what is in the Survey.

Bottom line, we must all get behind the new Decadal Survey if we have a chance of having the kind of program that it delineates. If the planetary community becomes divided over the results of the Survey, then I can guarantee that we will have dreams not realized.

Every year, I do a post looking at the President's budget proposal for NASA and its implications for future planetary exploration. This year, we have two competing budget narratives: the President's and one from the Republican-controlled House in Congress.

Because the President's just released budget proposal has more detail, we'll begin by looking at it. For FY12, which starts October 1 of this year, the President proposes to increase science spending at NASA by about $500M compared to FY10. (There is no approved budget for FY11, and agencies are currently funded at FY10 levels.) The increase is generally split between Earth Science and Planetary Science with other programs approximately flat. The bump in the Planetary program appears to be largely devoted to supporting the FY12 costs of the Mars Science Laboratory and the Mars MAVEN orbiter development, which hits its peak funding that year.

Beyond FY12, the President proposes to decrease Planetary Science spending, principally by decreasing spending in the Mars and lunar planetary programs. The Discovery and New Frontiers programs would receive modest increases, and other programs would remain approximately flat.

On-going missions such as Cassini and the various missions already at Mars would be funded

For the third year in a row, the budget proposal includes funding to start up new production of Plutonium 238 to support outer solar system missions.

The Discovery and New Frontiers projected budgets would support approximately 3 and 2.5 missions respectively (assuming continued funding through 2021 at projected FY16 rates and a fully burdened cost to NASA of ~$800M and ~$1.2B respectively for each mission)

In other NASA budget news, the Republican leadership in the House has proposed holding the NASA FY11 science funding (which is still not approved almost half way into the year) at FY10 levels. While Congress looks at budgets one year at a time, the Republican leadership has discussed a budget freeze in out years, leading to effective slow budget cuts as inflation takes its bite. If carried through for the next several years, and if funds for NASA's science programs remain at the same proportion as in FY10, this might mean higher Planetary budgets than the President has proposed.

Editorial Thoughts: Budget politics in the U.S. this year should be either entertaining or nail-biting depending on whether or not you depend of federal budgets for funding. The President's proposal probably represents the upside potential, and the House proposal the downside, and a split near the middle certainly is possible.

For readers who are not American, our budget process is interesting. The President proposes a budget, and then each house of Congress (the House is currently controlled by the opposition party, the Senate by the President's party) writes its own budget. Then, through negotiations, the three budget writing parties agree on a compromise that is passed as a law by Congress and signed by the President. When the process doesn't work, the government generally is funded under a continuing resolution that typically extends the previous year's funding levels.

Budget projections beyond FY12 have far less certainty than even the FY12 proposals. An interesting experiment is to compare last year's projections with this years, as I did with the dashed line in the first figure. That dashed line represents the projected spending for the Planetary Program in the Presiden'ts FY11 budget proposal.

Correction: A letter written by James Green, Director of NASA's Planetary Science Program, clarifies that the projected budgets for years beyond the current FY12 budget may be increased if necessary to accommodate the Survey's recommendations. The notes in the budget documents from which I drew my analysis suggested this possibility, but in a political climate promoting flat or declining budgets for federal programs, I did not place sufficient emphasis on this. I stand corrected, and this position is more encouraging for a vigorous program in the coming decade. I've retained the paragraphs that follow which appeared in the original post as an analysis of possible implications if future budgets were to decline as suggested by the out year budget projections.

After accounting for the Discovery, New Frontiers, research, and technology programs, there appears to be around $2.5B plus a bit to support additional missions assuming the projected FY16 budget continues through 2021. A ~$2.5B wedge would probably support the 2016 and 2018 joint Mars missions with ESA. It might support a scaled back version of the Jupiter Europa Orbiter. Without the decline in the Mars program budget (which could be targeted to other missions), the wedge might be another $2B+ larger.

In the press call on the budget, the head of NASA's science program emphasized that the implications of the budget of future planetary missions is well understood. To paraphrase him, they know that there is not enough funding for a full Discovery program, a full New Frontiers program, a full Mars program, a full outer planets program, etc. The goal of the Decadal Survey is to decide what should be funded within the budgets expected. The budget amounts and categories above are not fixed. In theory, the Survey could recommend ending the Discovery and New Frontiers programs to fund Flagship scale missions for Mars and the outer planets. (Not an outcome I expect.)

Thursday, February 10, 2011

The atmospheres around planets contain clues on the conditions in which those planets formed and on how they have evolved. As a result, missions to place probes into planets have remained a high priority since planetary exploration began. To date, the atmospheres of Venus, Mars, and Jupiter have been explored in situ by probes. (In the case of Mars and to a lesser extent Venus, landed missions have conducted composition and structure measurements.) The Mars Science Laboratory due to land next year will make new and more precise measurements of that world's atmosphere. If selected in the current New Frontiers competition, the Venus SAGE lander would act as an atmospheric probe during its descent. The Neptune and Uranus mission concepts include atmospheric probe options to extend measurements to the ice giants.

The Saturn probe mission concept proposes to return to the gas giants with a probe that would complement the Galileo probe's measurements at Jupiter. In some key respects, the Galileo probe was unable to fulfill its goals because it had the bad luck to descend through a dry atmospheric "desert" that was atypical of the planet. A mission to deliver a new probe (actually two) to Jupiter was prioritized in the last Decadal Survey. Unfortunately, the facilities to test probes for the harrowing entry into Jupiter's atmosphere no longer exist. (A portion of the probe mission's goals now will be performed through remote sensing by the Juno mission.)

Saturn in a way substitutes as a next best option to a new Jupiter probe -- it is the only other gas giant in the solar system. However, a probe mission to Saturn also would be a compliment. Saturn is believed to have formed in an adjacent region to Jupiter, and a probe's measurements would help scientists better model conditions in the early solar system. Measurements could help determine the mechanisms by which the gas giants formed. In particular, measurements of the abundances of heavier elements would help determine the mechanisms of gas giant formation.

The mission concept prepared by the Decadal Survey is probably the simplest of all the concept missions. A carrier/relay craft with the probe would arrive at Saturn approximately seven years after launch. Thirty days or more before arrival, the probe separates from the carrier/relay craft. The probe would enter the atmosphere and begin measurements at 0.1 bars (a bar is the atmospheric pressure at sea level on Earth). At 1 bar, the probe would detach from its parachute for a more rapid descent to 5 bars and the end of the nominal mission after 55 minutes of data collection. The probe would be designed to survive to 10 bars, and the carrier/relay would continue to listen for as long as the entry site remains visible.

The Decadal Survey requested that the study team consider only the simplest mission with a single atmospheric probe and just two instruments: a mass spectrometer and an atmospheric structure instrument. With just this core mission, the estimated cost would fit into the FY15 New Frontiers mission cost.

The study team notes that an actual mission team might well suggest additional instruments. From previous studies, additional instruments such as nephelometer to study clouds and haze structure or a net flux radiometer to study energy balance would be among several candidates. One addition might be a module attached to the probe with a microwave radiometer to conduct deep remote sensing measurements of the atmosphere similar to Juno prior. (The module would be jettisoned just before entry.) If funds permit, a second atmospheric probe likely would be a high priority.

Editorial Thoughts: The arguments for atmospheric probes as high priority missions have long been convincing to me. I hope that the Decadal Survey will propose at least one probe mission. For me, a Venus probe to better understand the formation of terrestrial worlds and the unique evolution of that world would be highest priority. (The 1978 Venus Pioneer probes left many unanswered questions that modern instruments could address.) I would then prioritize a probe to Uranus or Neptune second to explore a different class of worlds. However, if budgets or the Decadal Survey members better understanding of research priorities results in a Saturn probe, this would be a mission I would whole heartedly support.

There is just one addition that I really would like to see added. Cameras are now relatively cheap and lightweight. A camera on the back of the aeroshell and on the probe to take images before and after entry could produce some of the most beautiful images in planetary exploration. Think of the rings seen from just above or within the atmosphere. A 2006 Saturn probe summary listed an imager as a possible instrument, so this may not be an impossible wish.Appendix: Science Objectives

The following objectives, copied from the concept study report, are similar to the goals for most atmospheric probe missions. With some minor changes, they could be applied to probe missions to Uranus and Neptune. A Venus probe mission would have goals that echo these but also would be focused on chemical interactions with the surface and evolution of the atmosphere's composition.

Determine the vertical profile of zonal winds as a function of depth at the probe descent location**

Determine the location, density, and composition of clouds as a function of depth in the atmosphere**

Determine the variability of atmospheric structure and presence of clouds in two locations**

Determine the vertical water abundance profile at the probe descent location**

Determine precision isotope measurements for light elements such as S, N, and O found in simple atmospheric constituents

*Results would be enhanced with microwave radiometer measures of atmospheric structure prior to probe entry to obtain measurements at depths greater than probe will reach while operating (less useful at Uranus and Neptune because of depth of key structures)**Measurements from multiple probes would enhance results

Sunday, February 6, 2011

The European Space Agency reviewed the status of its three candidates for its large (700M Euro) mission selection slated for this June. Articles on the journal Nature's website and Space News's website summarize the issues facing ESA in the selection. Whichever mission is selected is expected to launch around 2022 (which is two years later than I recall, but I haven't been following that date closely).

Three missions are in contention:

Jupiter Ganymede Orbiter (JGO) - Would orbit Ganymede following an intensive campaign of Callisto flybys. Would compliment a NASA Jupiter Europa Orbiter (JEO) if that mission is prioritized by the Decadal Survey and funded by Congress, but could also fly as a standalone mission. Apparently no technology readiness issues. Estimated cost: 710M Euros.

International X-ray Observatory (IXO) - A next generation X-ray astronomy mission that requires contributions from both NASA and the Japanese space agency, JAXA. The two articles make it clear that the mission depends on novel X-ray optics, but less clear on whether these optics still represent a technology development risk. ESA estimated cost: 660M Euros.

Laser Interferometer Space Antenna (LISA) - Three spacecraft would fly in formation to become a highly sensitive gravity wave observatory. The technical challenges behind this mission are substantial, and ESA plans to fly a technology demonstration mission in 2013. NASA contributions apparently would be required to fly the mission. ESA estimated cost: 750M Euros.

The ESA costs do not include the funding of instruments that are usually paid for separately by ESA member nations sponsoring individual instruments.

The articles stress that a key challenge for the ESA selection will be lack of commitment from NASA and JAXA for their contributions to IXO and LISA. The recently completed U.S. astronomy and astrophysics Decadal Survey did not make either mission a top priority, but left open the possibility of a NASA collaboration. If ESA selects either mission, NASA would have to find funds in its budget to support the mission and Congress would have to approve the funding. (I don't understand the Japanese budget approval process and don't know how easy or difficult securing its commitment to IXO might be.)

Editorial Thoughts: Perhaps the hardest part about international collaborations for space missions is aligning the decision making and funding processes of multiple space agencies. From these articles, it appears that ESA would be taking something of a leap of faith to select either IXO or LISA this summer in terms of international partner commitments and technology readiness. From that perspective, JGO might be the programmatically least risky choice. Should NASA not proceed with its JEO, then ESA would have the exploration of the Jovian icy ocean worlds to itself for the coming two decades. (I suspect that if JGO is selected and JEO is not flown, that JGO's mission goals would be expanded to include flybys of Europa. I've been told by a JPL mission planner that enhancing a Ganymede orbiter to perform Europa flybys should be relatively straightforward to do.) ESA will have the benefit of knowing NASA's planetary priorities (expected announcement in March) before making its large mission selection.

However, if ESA selects either IXO or LISA, there likley would be considerable pressure on NASA to find funds to support the mission -- both would be great missions. NASA is also considering partnering with ESA on other astronomy/astrophysics missions, and a larger program of cooperation might be put on the table.

Issues of international collaboration also may influence NASA's planetary priorities. NASA and ESA have a cooperative Mars program that currently includes the 2016 Mars Trace Gas Orbiter (MTGO) and the 2018 ExoMars and MAX-C rovers. It's unclear whether MTGO is a committed mission or is subject to Decadal Survey prioritization, but the 2018 rovers mission clearly will be among the missions that the Decadal Survey will prioritize. ESA does not have the funding to fly the ExoMars mission on its own -- it depends on a NASA launch and a NASA entry, descent, and landing vehicle. That puts the Decadal Survey in the position of either funding its contribution (I have not seen an estimate, but it would be hundreds of millions of dollars) or leaving the ExoMars rover -- an excellent mission -- stranded. The decision of whether to fly the NASA MAX-C rover as the first element of a Mars sample return campaign may be made separately. The Survey could recommend no 2018 Mars mission and leave ExoMars stranded, flying the 2018 mission with the ExoMars rover only, ExoMars and a NASA geophysical station, ExoMars with NASA's MAX-C rover, or ExoMars with NASA's MAX-C rover and a simple NASA geophysical station. (Hey, if all this was easy, there would be no need for this blog and I would have to find another advocation.)

Mars program planning aside, the two articles mentioned above make me more hopeful about the chances of JGO being ESA's selection is summer.

The concept has many simularities to the Io Volcano Observer Discovery proposal that I wrote about almost two years ago. This is not surprising since both take their starting point from the same JPL concept study conducted in 2008. The mission would place an spacecraft into a highly inclined (>45 degree) orbit around Jupiter that would encounter Io at each perijove. The inclined orbit keeps the spacecraft out of the highest radiation fields except during the actual flyby. This strategy allows the mission to avoid the high-cost radiation mitigation strategies of the proposed Jupiter Europa mission and instead use the more modest design approaches employed by the upcoming Juno Jupiter orbiter. (The Io Observer would have less than half the radiation exposure of Juno by the end of their nominal missions.)

At each Io flyby, the spacecraft would map the illuminated hemisphere in eight colors at resolutions of less than 1 km/pixel. Selected areas would be mapped at 10-100 m/pixel in four colors and small areas at less than 10 m in panchromatic. A thermal mapper would provide high resolution thermal imaging of the moon during the flybys and whole disk heat flow maps at ~200 km/pixel when Io slips into Jupiter's shadow and the spacecraft is between flybys. Observations of Jupiter's atmosphere could also be made between flybys.

The six to ten encounters in the nominal mission would employ a variety of encounter strategies at Io. There would be at least three passes each on the day and night sides of Io. Two flybys would study magnetic induction by conducting encounters at high but opposite magnetic latitudes. Two or more flybys would encounter Io at the same latitude to allow searches for changes on the surface. At least one flyby would occur below 100 km above the surface, and one encounter might take the spacecraft through a volcanic plume.

The instrument list proposed would be modest: a narrow angle camera with filters for multispectral imaging, a thermal mapper operating between 2-20 μm, an ion and neutral mass spectrometer to measure the composition of material ejected from Io, and a magnetometer. One option studied would add a fast-imaging plasma spectrometer to map the distribution of ions in the space around Io. Charts tying science goals to instruments note that an ultraviolet spectrometer and a near-IR spectrometer also would make valuable contributions (with the latter also noted as useful for studies of the Jovian atmosphere).

The Io Observer Decadal Survey concept and the Io Volcanic Observer Discovery concept have two key differences. The analysis for the Survey concept concluded that solar power was more practical than plutonium ASRGs. The Discovery concept was based on ASRGs. At the time the Discovery concept was publicly discussed, it would have been powered by ASRGs. That concept's study, however, was funded to determine the types of missions that would be enabled by ASRG units. I understand that the PI submitted a proposal to the current Discovery mission selection; I don't know what power source was proposed. An advantage for proposing an ASRG system for a Discovery proposal would be that NASA would pick up the costs for the ASRGs but not for solar panels. In addition, ASRG's would allow all instruments to be mounted to the spacecraft body, while solar panels would require the remote sensing instruments to be mounted on a more expensive scan platform.

The second key difference between the two concepts is in the cost estimates. The Survey concept would fit within a New Frontiers budget while the Discovery concept would cost several hundred million dollars less. Yet the two concepts appear quite similar. It could be that the team estimating the Survey concept was too conservative -- under the ground rules established by the Survey, conservative estimates were encouraged and each concept had to carry hefty cost reserves. The PI for the Discovery concept may be too optimistic, although he is very experienced and has well established credibility. A similar difference exists between the Survey's Titan lake probe cost estimates in the small Flagship range and a similar Discovery proposal, with the Discovery proposal again led by a very experienced, credible team. Several of the Survey concept reports speculated that it might be possible to significantly reduce costs below their estimates with a focused design-to-cost approach.

Appendix: Science goals from the report

"Understand the eruption mechanisms for Io’s lavas and plumes and their implications for volcanic processes on Earth, especially early in Earth’s history when its heat flow was similar to Io’s, and elsewhere in the solar system.

"Determine Io’s interior structure, e.g., whether it has a magma ocean, and implications for the coupled orbital-thermal evolution of Io and Europa.

"Investigate the processes that form Io’s mountains and the implications for tectonics under high heat-flow conditions that may have existed early in the history of other planets.

"Understand the composition, structure, and thermal structure of Io’s atmosphere and ionosphere, the dominant mechanisms of mass loss, and the connection to Io’s volcanism.

"Determine whether Io has a magnetic field.

"Understand Io’s surface chemistry, including volatiles and silicates, and derive magma compositions (and ranges thereof), crustal and mantle compositions and implications for the extent of differentiation, and contributions to the atmosphere, magnetosphere, and torus."

"Improve our understanding of Jupiter system science, including meteorology, aerosol structure, tropospheric composition, and auroral phenomena on Jupiter, composition and temporal variability of Europa’s exosphere, Jovian magnetospheric processes, and small inner moons and rings of Jupiter."

Wednesday, February 2, 2011

Approximately twice a year, the National Academy of Sciences Planetary Science Subcommittee meets and reviews status and issues in NASA's planetary program. The most recent meeting just completed, and I will summarize highlights. The meetings typically have an update from NASA's headquarters, special presentations on key issues, and updates from the analysis groups (Outer planets (OPAG), Mars (MEPAG), Venus (VEXAG), lunar (LEAG), and small bodies (SBAG)). You can view the presentations at www.lpi.usra.edu/pss/jan2011

Much of the meeting consisted of status updates, but four issues seemed to stand out:

1) NASA (and most Federal programs) do not know what their budget will be this year or for coming years. They are reacting by being conservative both by mandate (e.g., no new initiatives such as the restart of plutonium 238 production) and judgement (e.g, being careful not to over commit research grants).

2) There still is no plan to restart plutonium 238, which is essential to exploring the outer solar system beyond Jupiter for simpler missions and at Jupiter for Flagship missions.

3) Launch vehicle costs are rising (see below). In an era of expected flat to declining budgets, this translates into fewer missions.

4) Mars Science Laboratory (Curiosity) costs are expected to require more funds. NASA plans to first take funding from JPL, the implementing organization, then the Mars program, and finally the larger planetary program.

The number of missions being proposed or under development (Venera-D) suggest that Venus may again become a priority destination. In addition to the two ESA Cosmic Vision proposals for Venus, I know of proposals for a Titan balloon and a Uranus orbiter. There are likely additional planetary proposals. The selected mission would launch in the early 2020s.

The MESSENGER spacecraft is expected to have fuel for a second year of studies in orbit. NASA is beginning planning to decide whether to fund a second year of operations.

It is possible (probable?) that the Decadal Survey will recommend only one of the two large Flagship missions proposed for the next decade, the Jupiter Europa Orbiter or the MAX-C rover that would cache samples for a Mars sample return mission. This slide acknowledges that the plans for outer planet exploration may have to be reset if JEO is not recommended.

The Mars program has become a joint NASA-ESA program that is planning a sequence of missions that include ESA's ExoMars rover, NASA's MAX-C rover, and future missions to return samples. The international cooperation may influence the Decadal Survey's recommendations for priority missions. If Mars missions are not a recommended priority, then the Mars community is likely to be rethinking its program.

An example of the cost increases NASA is facing for launching missions.

About Me

You can contact me at futureplanets1@gmail.com with any questions or comments.
I have followed planetary exploration since I opened my newspaper in 1976 and saw the first photo from the surface of Mars. The challenges of conceiving and designing planetary missions has always fascinated me. I don't have any formal tie to NASA or planetary exploration (although I use data from NASA's Earth science missions in my professional work as an ecologist).
Corrections and additions always welcome.